Metal impregnated zeolite adsorbents, methods of making, and systems for using the same

ABSTRACT

Metal exchanged and impregnated zeolite materials, methods for making metal exchanged and impregnated zeolite materials, and systems for reducing an amount of a contaminant species in a feed stream using a metal exchanged and impregnated zeolite material are provided. An exemplary metal exchanged and impregnated zeolite material comprises a metal exchanged zeolite material with the formula ((M 2/n O) a •(M′ 2/n′ O) a′ )•Al 2 O 3 •bSiO 2 ; and a metal oxide with the formula M 2/n O impregnated in the metal exchanged zeolite material such that the metal oxide is contacting an interior surface of the pore structure of the metal exchange zeolite material. In this example, M is a cation of an alkali or alkaline earth metal, n is a valence state of metal cation M, M′ is a cation of a metal other than an alkali or alkaline earth metal, n′ is a valence state of metal cation M′, 0≦a&lt;1, 0&lt;a′≦1, a+a′=1, and b is about 2 to about 500.

TECHNICAL FIELD

The technical field generally relates to zeolite adsorbent materials,methods of making, and systems for using the same. More particularly,the technical field relates to metal impregnated zeolite adsorbentmaterials, methods of making, and systems for using the same.

BACKGROUND

Zeolites are microporous, aluminosilicate materials commonly used ascommercial adsorbents and catalysts. Zeolites owe their adsorbentcapacity to their regular pore structure of molecular dimensions. Thisregular pore structure provides zeolites an ability to selectively sortmolecules based primarily on a size exclusion process.

When in an acid form, zeolite materials are also capable of catalyzingcertain reactions, such as oligomerization and isomerization ofcomponents of many olefinic streams. Further, when used to remove orreduce undesired species from a reactive olefinic stream, zeoliticmaterials are subjected to repeated harsh regeneration cycles that occurduring the life of the adsorbent. The conditions of the regenerationcycles encourage catalytic activity of the adsorbent, which leads todiminished adsorbent capacity and limited life span due to coking.

Unfortunately, certain zeolite materials that are otherwise suitable forremoval or reduction of certain undesired compounds that may be presentin an olefinic stream, such as organic sulfur-containing species, areparticularly susceptible to problems arising from reacting withcomponents in the olefinic stream. For instance, ZnX is an 80% ionexchanged Zn-based X-type zeolite which contains about 15% Zn on avolatile free basis. ZnX shows excellent organic sulfur removal behaviorwhen used as an adsorbent for olefin streams. However, ZnX also displayshigh reactivity with olefins in terms of isomerization andoligomerization, leading to significant problems with coking andshortened lifespan. Thus, ZnX's reactivity with olefins limits ZnX'sutility as an adsorbent for use with olefinic streams.

Accordingly, it is desirable to provide zeolites with satisfactoryadsorbent behavior but reduced reactivity for use with olefinic streams.In addition, it is desirable to provide methods and systems for usingsuch zeolites. Furthermore, other desirable features and characteristicsof the present invention will become apparent from the subsequentdetailed description and the appended claims, taken in conjunction withthe accompanying drawings and this background.

BRIEF SUMMARY

Metal exchanged and impregnated zeolite materials, methods for makingmetal exchanged and impregnated zeolite materials, and systems forreducing an amount of a contaminant species in a feedstock using a metalexchanged and impregnated zeolite material are provided herein. In anexemplary embodiment, a metal exchanged and impregnated zeolite materialcomprises a metal exchanged zeolite material with the formula((M_(2/n)O)_(a)•(M′_(2/n′)O)_(a′))•Al₂O₃•bSiO₂; and a metal oxide withthe formula M_(2/n)O impregnated in the metal exchanged zeolite materialsuch that the metal oxide is contacting an interior surface of the porestructure of the metal exchange zeolite material. In this embodiment, Mis a cation of an alkali or alkaline earth metal, n is a valence stateof metal cation M, M′ is a cation of a metal other than an alkali oralkaline earth metal, n′ is a valence state of metal cation M′, 0≦a<1,0<a′≦1, a+a′=1, and x is about 2 to about 500.

In another exemplary embodiment, a method for making a metal exchangedand impregnated zeolite material comprises admixing a solid zeolitecomprising metal cation M occupying metal exchange sites in the solidzeolite and a solid salt comprising a metal cation M′ to form a solidsalt/zeolite mixture, where M is a cation of an alkali or alkaline earthmetal and M′ is a cation of a metal other than an alkali or alkalineearth metal; and heating the solid salt/zeolite mixture in the absenceof liquid water to a temperature sufficient for metal cation M′ tomigrate and exchange into at least a portion of the metal exchange sitesin the solid zeolite to form a metal exchanged and impregnated zeolitematerial that is impregnated at least with an oxide comprising metalcation M. In this embodiment, the solid salt has a melting temperatureat or below a temperature at which a pore structure of the solid zeoliteis damaged, and the solid salt/zeolite mixture is heated to atemperature at or below a temperature at which a pore structure of thesolid zeolite is damaged.

Also provided herein are systems for reducing an amount of a contaminantspecies in a feed stream. In an exemplary embodiment, a system comprisesa column configured to contain a metal exchanged and impregnated zeolitematerial, and further configured to receive and contact a feed streamwith the metal exchanged and impregnated zeolite material underconditions effective for at least a portion of a contaminant species inthe feed stream to be adsorbed by the metal exchanged and impregnatedzeolite material. In this embodiment, the metal exchanged andimpregnated zeolite material comprises a metal exchanged zeolitematerial with the formula ((M_(2/n)O)_(a)•(M′_(2/n′)O)_(a′))•Al₂O₃•bSiO₂; and a metal oxide with the formulaM_(2/n)O impregnated in the metal exchanged zeolite material such thatthe metal oxide is contacting an interior surface of the pore structureof the metal exchange zeolite material, where M is a cation of an alkalior alkaline earth metal, n is a valence state of metal cation M, M′ is acation of a metal other than an alkali or alkaline earth metal, n′ is avalence state of metal cation M′, 0≦a<1, 0<a′≦1, a+a′=1, and x is about2 to about 500.

DETAILED DESCRIPTION OF THE DRAWINGS

The various embodiments will hereinafter be described in conjunctionwith the following drawing figures, wherein like numerals denote likeelements, and wherein:

FIG. 1 is a schematic illustration of a system for reducing the amountof a contaminant species in a feed stream in accordance with anexemplary embodiment.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit the various embodiments or the application anduses thereof.

Furthermore, there is no intention to be bound by any theory presentedin the preceding background or the following detailed description.

Metal impregnated zeolite adsorbents, methods of making, methods ofusing, and systems for using the same are described herein. Metalimpregnated zeolite materials described herein may be used asadsorbents, such as for removal or reduction of organic sulfur compoundsfrom an olefinic stream, while exhibiting reduced reactivity towardsolefins.

Zeolites are crystalline aluminosilicate compositions which aremicroporous and which have a three-dimensional oxide framework formedfrom corner sharing AlO₂ and SiO₂ tetrahedra. Zeolites are characterizedby having pore openings of uniform dimensions, having a significant ionexchange capacity, and being capable of reversibly desorbing an adsorbedphase which is dispersed throughout the internal voids of the crystalwithout significantly displacing any atoms which make up the permanentzeolite crystal structure. In some embodiments, zeolites are those whichhave a pore opening of about 5 Å to about 10 Å.

In general, zeolites have a composition represented by the empiricalformula (on a water free basis) M_(2/n)O•Al₂O₃•bSiO₂, where M is acation having a valence of “n”, and “b” has a value of about 2 to about500. Typically, cations M in conventional as-synthesized zeolites may bealkali metals, alkaline earth metals, hydrogen ions, ammonium ions, ormixtures thereof. However, in embodiments provide herein, cations M inzeolite starting materials are typically cations of an alkali oralkaline earth metal. In some embodiments, zeolites have a SiO₂/Al₂O₃ratio of about 2:1 to about 6:1 (that is, b has a value of about 2 toabout 6), and/or have a crystal structure of zeolite X, faujasite,zeolite Y, zeolite A, mordenite, beta, and ferrierite. Various processesfor preparation of zeolites are well known in the art.

The zeolite three-dimensional oxide framework carries a negative charge,and requires that a quantity of cations M be present in the channelsand/or pores to balance the charge. However, as the cations M are notpart of the framework, they are exchangeable and are said to occupyexchange sites within the zeolite. Metal exchange is typically carriedout via a solution ion exchange process, which involves contacting azeolite with a solution containing a dissolved cation under conditionssuch that the dissolved cation M′ from the ion exchange solutiondisplaces (i.e., is exchanged for) a cation M already present in thezeolite. In solution ion exchange processes, cation M′ typically is ametal cation of an alkali, alkaline earth, various transition, or rareearth metal.

Specific ion exchange solutions and conditions for typical solutionexchange processes vary depending on the particular zeolite and desiredcation to be exchanged. For instance, certain cations have limitedsolubility in basic or neutral ion exchange solutions. So, in order toachieve a sufficiently high concentration of the cation to be exchangedin the ion exchange solution, an acidic ion exchange solution isprepared. However, contacting the zeolite with an acidic ion exchangesolution, coupled with the Lewis acidity of the cation to be exchangeditself, generates significant reactive acidic hydroxyl groups on theinternal and external surfaces of the zeolite. Further, in solution ionexchange processes, the exchanged cations M from the zeolite leave thezeolite structure and migrate into the ion exchange solution, with atleast a portion ultimately leaving the pore structure of the zeolite.Removal of the exchanged cations leads to a further reduction of basiccharacter on the internal and external surfaces of the zeolite, furtherallowing generation of the acidic hydroxyl groups. Without wishing to bebound by theory, it is believed that these acidic hydroxyl groups leadto high reactivity of the resulting acidic ion exchanged zeolite witholefins.

In embodiments, methods of preparing zeolite materials as describedherein avoid, or at least reduce, this problem. Specifically, exemplaryembodiments of methods of preparing zeolite materials as describedherein do not rely on an acidic ion exchange solution for cationexchange. Rather, exemplary embodiments of methods described herein usesolid state techniques such that the zeolite is not contacted with anacidic solution during ion exchange. Further, in some embodimentsmethods of preparing zeolite materials as described herein are used toprepare exchanged and impregnated zeolite materials. As previouslydiscussed, cation exchange in a zeolite material is where at least aportion of cations M present in exchange sites within the zeolitecrystal structure are replaced with a second cation M′. This is distinctfrom impregnation, where one or more chemical species are present withinthe pore structure of the zeolite material such that the one or morechemical species contact an interior surface of the pore structure.

In the materials described herein, metal cations M and M′ are differentmetal cations. In some embodiments, metal cation M is a cation of analkali or alkaline earth metal. In some specific embodiments, metalcation M is a sodium cation. In some embodiments, metal cation M′ is acation of a metal other than an alkali or alkaline earth metal, such asa transition or rare earth metal. In some specific embodiments, metalcation M′ is a cation of copper, iron, manganese, silver, or zinc. Insome specific embodiments, metal cation M′ is a zinc cation. In someembodiments, the one or more impregnated chemical species are one ormore oxides comprising metal cation M, or a combination of one or moreoxides comprising metal cation M and one or more oxides comprising metalcation M′.

Thus, in some embodiments, a metal impregnated and exchanged zeolitematerial comprises a metal exchanged zeolite material and a metal oxidepresent in the metal exchanged zeolite material such that the metaloxide contacts an interior surface of the pore structure of the metalexchanged zeolite material. In these embodiments, the metal exchangedzeolite comprises one or more metal cations (e.g., M′ or a combinationof M and M′) present in exchange sites within the metal exchangedzeolite, and one or more impregnated oxides comprising metal cation M,or a combination of one or more oxides comprising metal cation M and oneor more oxides comprising metal cation M′, contacting an interiorsurface of the pore structure of the metal exchanged zeolite material.In some embodiments, both metal cation M and metal cation M′ occupymetal exchanged sites within the metal exchanged zeolite. In otherembodiments, the extent of exchange is about 100%. That is, in someembodiments metal exchanged zeolites comprise only metal cations M′ inmetal exchange sites.

Exemplary methods of preparing metal impregnated and exchanged zeolitematerial will now be discussed. In some embodiments, a solid zeolitematerial powder or cake (comprising metal cation M in metal exchangesites) is contacted with a salt comprising a metal cation M′ to beexchanged into the zeolite. This contact occurs in a dry environmentunder conditions such that metal cation M′ migrates from the salt intothe zeolite and exchanges with metal cation M such that at least aportion of metal exchange sites in the zeolite material become occupiedby metal cation M′. As used herein, the term “dry environment” means inthe absence of liquid water. Thus, in these embodiments, at least aportion of metal exchange sites formerly occupied by metal cation Mwithin the zeolite starting material become occupied with metal cationM′ without the zeolite material contacting an acidic solution. As thezeolite material does not contact an acidic solution during the exchangeprocess, generation of acidic hydroxyl groups on the interior andexterior surfaces of the zeolite is greatly reduced.

As metal cations M are exchanged with metal cations M′ at various metalexchange sites, the exchanged metal cations M remain in the pores of themetal exchanged zeolite materials as oxides of metal cation M. Forinstance, in embodiments where the starting solid zeolite material is asodium zeolite, the exchanged sodium ions remain in the pores of themetal exchanged zeolite material as impregnated sodium oxide (Na₂O).Again without wishing to be bound by theory, this impregnated Na₂O addsbasic character to the exchanged zeolite pore surface. It is believedthat this basic character further inhibits generation of acidic hydroxylgroups. As such, metal impregnated and exchanged zeolite materialsprepared according to exemplary embodiments of methods described hereinexhibit reduced reactivity with olefins relative to metal exchangedzeolites prepared via solution ion exchange.

Methods for preparing metal impregnated and exchanged zeolite materialvia a solid state impregnation technique include preparing a mixturecomprising a solid zeolite comprising a metal cation M and a solid saltcomprising a metal cation M′ to be impregnated into a zeolite, whereinmetal cation M and metal cation M′ are not the same. The mixture isheated in a dry environment to a temperature that allows for migrationof metal cations M′ from the solid salt into the zeolite structure andexchange with metal cations M. Metal cation migration and exchange mayoccur at temperatures below the melting point of the solid salt.However, heating to a temperature of at least at or about the meltingpoint of the solid salt facilitates metal cation migration.Additionally, each zeolite material has a temperature above which thezeolite pore structure is damaged. The temperature for metal cationmigration and exchange is generally selected to be at or below thetemperature at which zeolite damage occurs.

Thus, in some embodiments, the mixture is heated to a temperature of atleast at or about the melting point of the solid salt but below atemperature at which the zeolite structure is damaged, and held at atemperature within this range for a time sufficient for metal cations M′from the solid salt to migrate and exchange into the metal exchangesites of the zeolite structure. Times and temperatures of specificembodiments will vary depending on a number of conditions, including themetal cations M and M′, the specific solid salt employed, the particularzeolite, and the desired degree of exchange.

Specific solid salts useful in the present methods include those whichcomprise a metal cation M′ that is desired for exchange into thezeolite, and which have a melting point at or below about a temperatureat which the zeolite structure is damaged. Suitable salts may includechloride, nitrate, or acetate salts of the desired metal. However, thislist is not intended to be limiting as numerous salts of a desired metalmay exist that have a melting point at or below the temperature at whicha zeolite structure is damaged.

The relative amounts of solid salt and zeolite in the solid salt/zeolitemixture may vary depending on the particular salt and zeolite, thedesired degree of exchange, and the intended thermal processingconditions (e.g., time and temperature). In some embodiments, solidsalt/zeolite mixtures are prepared such that the mixture has a moleratio of solid salt to zeolite of between about 0.5:1 to about 2:1, suchas about 1:1. For some zeolite materials, the temperature at which thezeolite structure is damaged is about 800° C. Thus, in some embodiments,the solid salt/zeolite mixture is heated to a temperature sufficientlyhigh to allow for migration and exchange of the metal cation M′ from thesalt into the metal exchange sites of the zeolite structure, with thattemperature not exceeding about 800° C. In some embodiments, the solidsalt/zeolite mixture is heated to a temperature of about 50° C. to 800°C., such as about 50° C. to 600° C., such as about 50° C. to 400° C.,such as about 200° C. to 400° C. The solid salt/zeolite mixture is heldat this elevated temperature for a sufficient time for the desireddegree of exchange to occur and cooled. As discussed above, as cationsof metal M′ are exchanged into metal exchange sites of the zeolitematerial, cations of metal M are displaced and form an oxide within thepore structure of the exchanged zeolite material, thus forming a metalexchanged zeolite (at least partially exchanged with metal cation M′)that is impregnated at least with an oxide comprising metal cation M.

In some embodiments, it is desirable for a metal impregnated andexchanged zeolite material to be prepared as a pellet or other bulksolid. Various conventional processes for preparing zeolites as pelletsor other bulk solids (such as via extrusion or granulation) may beutilized with the metal impregnated and exchanged zeolite materialsdescribed herein. Typical extrusion or granulation processes involvemixing a zeolite with a binder, pressing the mixture into a desiredshape, and heat treating the pressed material at a temperaturesufficiently high and for a sufficient time such that when the pressedmaterial is cooled the binder is set. In some embodiments, a metalimpregnated and exchanged zeolite material prepared as described aboveis mixed with a binder. This mixture can then be subjected to anysuitable forming process, such as extrusion or granulation, andprocessed to set the binder. Suitable binders may be determined by oneof skill in the art, and generally the temperature necessary to set thebinder is below the temperature at which a zeolite structure is damaged.Exemplary binders include, but are not limited to, clays, alumina,silica, aluminum silicate, inorganic cement, and various polymers.

In some alternate embodiments where the metal impregnated and exchangedzeolite material is to be prepared as a pellet or other bulk solid, abinder may be included in the solid salt/zeolite mixture prior tothermal treatment for metal exchange. In these embodiments, the solidsalt may be selected such that the melting point of the solid salt is ator below the temperature necessary to set the binder. In someembodiments, the methods include preparing a mixture of a solid saltcomprising a metal cation to be exchanged into a zeolite, a solidzeolite, and a binder. This mixture may then be subjected to a formingprocess, such as extrusion or granulation, and heated to a firsttemperature sufficient to allow metal cations from the solid salt tomigrate and exchange into the metal exchange sites of the zeolitestructure and thus form a metal impregnated and exchanged zeolitematerial as provided above.

In some embodiments, the first temperature is also sufficiently high toset the binder. In these embodiments, a solid salt/zeolite/bindermixture may be subjected to a single thermal processing step comprisingheating the mixture to a temperature for a sufficient length of timesuch that only the single thermal processing step is necessary for metalexchange and binder setting. In these embodiments, a suitabletemperature will depend on the identity of the solid salt and binder. Insome embodiments, a suitable temperature may be about 500° C. to about700° C., such as about 600° C. to about 700° C.

In some alternative embodiments, metal exchange and binder setting maybe conducted via a plurality of thermal processing steps. In thesealternative embodiments, a solid salt/zeolite/binder mixture issubjected to a first thermal processing step comprising heating to afirst temperature sufficiently high for a sufficient length of time toallow for migration and exchange of a metal cation M′ from the salt intothe metal exchange sites of the zeolite, as described above. In theseembodiments, the first temperature is not sufficiently high to set thebinder, thus this first thermal processing step forms a metalimpregnated and exchanged zeolite material/binder mixture. The metalimpregnated and exchanged zeolite material/binder mixture is thensubjected to a second thermal processing step comprising heating to asecond temperature sufficiently high for a sufficient period of time toset the binder. In these embodiments, the second temperature is higherthan the first temperature. In some related embodiments, a firsttemperature may be about 50° C. to about 600° C., such as about 50° C.to about 400° C., such as about 200° C. to about 400° C., and a secondtemperature may be about 600° C. to about 800° C., such as about 600° C.to about 700° C.

Thus in some embodiments, a solid salt/zeolite/binder mixture issubjected to a thermal treatment protocol comprising a first thermaltreatment step to form a metal impregnated and exchanged zeolitematerial/binder mixture, and a second thermal treatment step to set thebinder. In some embodiments, the metal impregnated and exchanged zeolitematerial/binder mixture is not cooled between the first and secondthermal processing steps. In alternative embodiments, the thermaltreatment protocol may be conducted such that the metal impregnated andexchanged zeolite material/binder mixture is cooled between two thermalprocessing steps.

In some embodiments, excess solid salt in the solid salt/zeolite mixturemigrates into the pore structure of the zeolite material. In theseembodiments, the resulting metal impregnated and exchanged zeolitematerial may further comprise residual solid salt starting materialoccluded in the pore structure. If the second thermal processing step isconducted at a sufficiently high temperature, subjecting a metalimpregnated and exchanged zeolite material/binder mixture to the secondthermal processing step as described above may have an added benefit ofconverting residual occluded solid salt to relatively unreactive oxidesof metal M′. Thus, in these embodiments, the metal impregnated andexchanged zeolite material may have one or more oxides comprising metalcation M and one or more oxides comprising metal cation M′ impregnatedin the pore structure of the final product. Formation of oxidescomprising metal cation M′ depends on the identity of the solid salt andspecific conditions of the second thermal processing step. Specifically,oxides comprising metal cation M′ will form if the thermal processingconditions are at a high enough temperature for a long enough period oftime to convert the residual solid salt to one or more oxides. Inembodiments where removal of residual occluded solid salts is desired,such as in embodiments where conversion of the residual solid salt tometal cation M′ oxides is not complete, a metal impregnated andexchanged zeolite material/binder mixture prepared as described hereinmay be washed with water to reduce the amount of residual occluded solidsalts present in the pore structure of the metal impregnated andexchanged zeolite material/binder mixture.

As provided above, the general chemical formula for a zeolite materialon a water free basis is M_(2/n)O•Al₂O₃ •bSiO₂, where n is the valencestate of metal cation M. Exchange of a second metal cation M′ into metalexchange sites of zeolite material results in a metal exchanged zeolitematerial with the general chemical formula of((M_(2/n)O)_(a)•(M′_(2/n′)O)_(a′))•Al₂O₃•bSiO₂, where M′ is the metalcation that has been exchanged into the zeolite material and n′ is thevalence state of metal cation M′. In some embodiments, about 10% toabout 100%, such as about 25% to about 100%, such as about 50% to about100%, such as about 75% to about 100%, such as about 90% to about 100%,of metal exchange sites in a metal impregnated and exchanged zeolitematerial prepared as described above will be occupied with metal cationM′.

As described above, metal cations M originally present in the zeolitemetal exchange sites that have been replaced with metal cations M′ donot depart the metal exchanged zeolite material. Rather, metal cations Mform oxides and remain impregnated in the pore structure contacting aninterior surface of the metal impregnated zeolite materials. Thus, metalimpregnated and exchanged zeolite material provided herein furthercomprise an impregnated metal oxide M_(2/n)O, wherein M is the metalcation that has been exchanged out of zeolite material, and the amountof metal oxide M_(2/n)O in the metal impregnated and exchanged zeolitematerial is proportionate to the extent of exchange of metal cation M′for metal cation M. Impregnated metal oxide M_(2/n)O is present in themetal exchanged zeolite material such that metal oxide M_(2/n)O contactsan inner surface in the pore structure of the metal exchanged zeolitematerial.

As described above, in some embodiments, not all of metal cation M′ thatmigrates into the metal impregnated and exchanged zeolite material isexchanged into a metal exchange site. In these embodiments, the metalimpregnated and exchanged zeolite material may further comprise animpregnated metal oxide M′_(2/n′)O. In some embodiments, the amount ofimpregnated metal oxide M′_(2/n′)O in a metal exchanged and impregnatedzeolite material may contain up to about 100%, such as up to about 75%,such as up to about 50%, such as about 0% to about 25%, or about 25% toabout 50% of the molar equivalent of metal cation M′ necessary to fullyoccupy the metal exchange sites in the zeolite material.

Numerous zeolite materials are known in the art, and methods describedherein for preparation of metal impregnated and exchanged zeolitematerials may be applied to any zeolite material without limit. In someembodiments, the zeolite starting material is a sodium zeolite with thegeneral chemical formula (on a water free basis) Na₂O•Al₂O₃•xSiO₂, wherex provides the molar amount of SiO₂ relative to Al₂O₃ present in thematerial. In some embodiments, the zeolite material starting material isthe zeolite material known in the art as 13X. Zeolite material 13X hasthe chemical formula Na₂O•Al₂O₃•2.5SiO₂•6H₂O.

The methods provided herein may be used to prepare any of a number ofexchanged and impregnated zeolite materials so long as a suitable solidsalt of the desired metal to be exchanged and optionally impregnated, asdescribed above, is available. Exemplary solid salt starting materialsmay include one or more alkali, alkaline earth, rare earth, and varioustransition metal cations. As provided above, use of such startingmaterials results in metal impregnated and exchanged zeolite materialswith at least a portion of metal exchange sites in the zeolite materialoccupied by the one or more alkali, alkaline earth, rare earth, andvarious transition metal cations from the solid salt starting material.

In some embodiments, exemplary solid salt starting materials include atleast one metal cation other than an alkali or alkaline earth metalcation. As provided above, use of such starting materials results inmetal impregnated and exchanged zeolite materials with at least aportion of metal exchange sites in the zeolite material occupied by theone or more metal cation other than an alkali or alkaline earth metalcation. In some particular embodiments, solid salt starting materialscomprise a copper, iron, manganese, silver, or zinc cation. As providedabove, use of such starting materials results in metal impregnated andexchanged zeolite materials with at least a portion of metal exchangesites in the zeolite material occupied by a copper, iron, manganese,silver, or zinc cation. It should be understood that this list is notintended to be limiting, as cations of numerous metals (or complex metalcations) are known to be able to be exchanged into a zeolite structure.

In some particular embodiments, the solid salt starting materialcomprises a zinc ion. Suitable zinc salts (i.e., those with suitably lowmelting temperatures) include, but are not limited to, zinc chloride,zinc nitrate, and zinc acetate. As indicated above, suitable thermaltreatment conditions will vary depending on the particular solid saltand zeolite material. In some exemplary embodiments, zinc may beexchanged into 13X by preparing a mixture comprising zinc chloride and13X. The mixture is then heated to a temperature of about 50° C. toabout 400° C., such as about 225° C., and held for a sufficient time forthe desired degree of exchange to occur. In one particular exemplaryembodiment, the mixture comprises zinc chloride and 13X at a mole ratioof about 1:1. This mixture is heated to about 225° C. and held for about4 hours. This particular set of conditions yields zinc impregnation intothe 13X of about 15% exchanged. However, the degree of zinc exchangecould be adjusted by increasing or decreasing the mole ratio of zincchloride to 13X, heating the mixture to a higher or lower temperature,holding the mixture at the elevated temperature for a longer or shorterperiod of time, or any combination thereof. In addition to being about15% zinc exchanged, the resulting zeolite material is impregnated withsodium oxide resulting from displaced sodium cations from metal exchangesites as discussed further below.

In some embodiments, methods described herein may be used to preparemetal exchanged and impregnated 13X such that zinc is exchanged into themetal exchange sites of the 13X at about 10% to about 100%, such asabout 25% to about 100%, such as about 50% to about 100%, such as about75% to about 100%, such as about 90% to about 100%. In some embodiments,zinc is exchanged at about 10% to about 100%, such as about 25% to about100%, such as about 50% to about 100%, such as about 75% to about 100%,such as about. In some related embodiments, the metal exchanged andimpregnated 13X may further comprise impregnated zinc oxide up to about100%, such as up to about 75%, such as up to about 50%, such as about 0%to about 25%, or about 25% to about 50% of the molar equivalent of zinccation necessary to fully occupy the metal exchange sites in the 13X.

At least a portion of the sodium cations displaced from metal exchangesites in the zinc exchanged 13X in these embodiments does not depart thezinc exchanged zeolite material. Rather, the sodium cations remainimpregnated in the pore structure of the zinc exchanged zeolite materialas sodium oxide. Thus, a zeolite material prepared as described above isa zinc exchanged and sodium impregnated 13X. In some embodiments, theratio of sodium to zinc to aluminum in the resulting zinc exchanged andsodium impregnated 13X is from about 2:0.1:2 (at 10% exchanged) to about2:1.5:2 (at about 100% exchanged with 50% additional zinc impregnation).In some embodiments, the ratio of sodium to zinc to aluminum is fromabout 2:0.25:2 to about 2:1.5:2, such as about 2:0.5:2 to about 2:1.5:2,such as about 2:0.25:2 to about 2:0.75:2, such as about 2:1:2 to about2:1.5:2. In some embodiments, the ratio of sodium to zinc to aluminum isfrom about 2:0.1:2 to about 2:1:2, such as about 2:0.25:2 to about2:1:2, such as about 2:0.5:2 to about 2:1:2, such as about 2:0.75:2 toabout 2:1:2, such as about 2:0.9:2 to about 2:1:2.

In other embodiments, methods and systems of reducing an amount of acontaminant species in a feed stream are provided. In these embodiments,a feed stream comprising a species capable of being adsorbed by themetal exchanged and impregnated zeolite materials described herein iscontacted with a metal exchanged and impregnated zeolite materialdescribed herein under conditions such that the metal exchanged andimpregnated zeolite material adsorbs at least a portion of thecontaminant species present in the feed stream. In some embodiments, thefeed stream is an olefinic feed stream, and the contaminant species isan organic sulfur containing species. In some embodiments, the metalexchanged and impregnated zeolite is a zinc exchanged and sodiumimpregnated zeolite material as described herein, such as a zincexchanged and sodium impregnated 13X as described herein.

An exemplary method of reducing an amount of a contaminant species in afeed stream will now be provided with reference to an exemplary systemas shown in FIG. 1. An exemplary system includes a column 2 configuredto contain one or more metal impregnated zeolite materials as describedherein 4. The column 2 is configured to receive a feed stream 6, andcontact the feed stream 6 with the one or more metal impregnated zeolitematerials 4 under conditions suitable for the adsorption of acontaminant species present in the feed stream 6. An output stream 8exits column 2 and contains less of the contaminant species than waspresent in the feed stream 6. In some embodiments, the feed stream 6comprises an olefinic feed stream. That is, in some embodiments, feedstream 6 comprises one or more olefins. In some embodiments, the one ormore metal impregnated zeolite materials 4 comprise a zinc exchangedzeolite material, such as a zinc exchanged sodium zeolite material, suchas a zinc exchanged 13X.

Note that reference to the specific arrangement in FIG. 1 is not meantto limit the apparatus and method to the details disclosed therein.Furthermore, FIG. 1 is a schematic illustration and does not show anumber of details for the process arrangement such as pumps,compressors, valves, and recycle lines that are well-known to thoseskilled in the art. For instance, in some embodiments, a system maycomprise a plurality of columns arranged in parallel, with each columnconfigured to contain one or more metal impregnated zeolite materials.As will be appreciated, such a configuration allows for one column to betaken off-line and the metal impregnated zeolite materials containedtherein to be regenerated or replaced, without disrupting feed streamflow to another column.

Those having skill in the art, with the knowledge gained from thepresent disclosure, will recognize that various changes could be made inthe compositions of matter, methods, and systems described hereinwithout departing from the scope of the present invention. Mechanismsused to explain theoretical or observed phenomena or results, shall beinterpreted as illustrative only and not limiting in any way the scopeof the appended claims.

What is claimed is:
 1. A metal exchanged and impregnated zeolitematerial comprising: a metal exchanged zeolite material with the formula((M_(2/n)O)_(a) •(M′_(2/n′)O)_(a))•Al₂O₃•bSiO₂; and a metal oxide withthe formula M_(2/n)O impregnated in the metal exchanged zeolite materialsuch that the metal oxide is contacting an interior surface of the porestructure of the metal exchange zeolite material; where M is a cation ofan alkali or alkaline earth metal, n is a valence state of metal cationM, M′ is a cation of a metal other than an alkali or alkaline earthmetal, n′ is a valence state of metal cation M′, 0≦a<1, 0<a′≦1, a+a′=1,and b is about 2 to about
 500. 2. The metal exchanged and impregnatedzeolite material of claim 1, further comprising a second metal oxidewith the formula M′_(2/n′)O impregnated in the metal exchanged zeolitematerial such that the second metal oxide is contacting an interiorsurface of the pore structure of the metal exchange zeolite material. 3.The metal exchanged and impregnated zeolite material of claim 1, whereinthe metal exchanged and impregnated zeolite material has a molar ratioof M:M′:Al of about (2/n):(0.2/n′):2 to about (2/n):(3/n′):2.
 4. Themetal exchanged and impregnated zeolite material of claim 1, whereinmetal cation M is a sodium cation.
 5. The metal exchanged andimpregnated zeolite material of claim 1, wherein metal cation M′ is acopper, zinc, manganese, silver, or iron cation.
 6. The metal exchangedand impregnated zeolite material of claim 1, wherein metal cation M is asodium cation and metal cation M′ is a zinc cation.
 7. The metalexchanged and impregnated zeolite material of claim 6, wherein the metalexchanged zeolite is zinc exchanged 13X.
 8. The metal exchanged andimpregnated zeolite material of claim 7, wherein the metal exchanged andimpregnated zeolite material has a molar ratio of Na:Zn:Al of about2:0.1:2 to about 2:1:2.
 9. The metal exchanged and impregnated zeolitematerial of claim 7, wherein the metal exchanged and impregnated zeolitematerial has a molar ratio of Na:Zn:Al of about 2:1:2 to about 2:1.5:2.10. A method for making a metal exchanged and impregnated zeolitematerial, the method comprising: admixing a solid zeolite comprisingcations of metal M occupying metal exchange sites in the solid zeoliteand a solid salt comprising a metal cation M′ to form a solidsalt/zeolite mixture, where metal cation M is a cation of an alkali oralkaline earth metal and metal cation M′ is a cation of a metal otherthan an alkali or alkaline earth metal; and heating the solidsalt/zeolite mixture in the absence of liquid water to a temperaturesufficient for metal cation M′ to migrate and exchange into at least aportion of the metal exchange sites in the solid zeolite to form a metalexchanged and impregnated zeolite material, wherein the metal exchangedand impregnated zeolite material is impregnated at least with an oxidecomprising metal cation M; wherein the solid salt has a meltingtemperature at or below a temperature at which a pore structure of thesolid zeolite is damaged, and the solid salt/zeolite mixture is heatedto a temperature at or below a temperature at which a pore structure ofthe solid zeolite is damaged.
 11. The method of claim 10, wherein thesolid salt/zeolite mixture is heated to a temperature at or above themelting temperature of the solid salt.
 12. The method of claim 10,wherein the solid zeolite and a solid salt are present in the solidsalt/zeolite mixture at a mole ratio of about 0.5:1 to about 2:1 solidsalt to zeolite.
 13. The method of claim 10, wherein the solid zeoliteis a sodium zeolite.
 14. The method of claim 12, wherein the solidzeolite is 13X.
 15. The method of claim 10, wherein the solid saltcomprises a zinc cation.
 16. The method of claim 15, wherein the solidsalt is selected from the group consisting of zinc chloride, zincnitrate, zinc acetate, and mixtures thereof.
 17. The method of claim 16,wherein the solid salt-zeolite mixture is heated to a temperature ofabout 200° C. to 400° C.
 18. The method of claim 10, further comprisingadmixing the metal exchanged and impregnated zeolite mixture with abinder to form a metal impregnated zeolite/binder mixture and heatingthe metal impregnated zeolite/binder mixture to a temperature sufficientto set the binder.
 19. The method of claim 10, wherein admixing a solidzeolite comprising metal cation M occupying metal exchange sites in thesolid zeolite and a solid salt comprising metal cation M′ to form asolid salt/zeolite mixture comprises admixing a binder with the solidzeolite and sold salt to form a solid salt/zeolite/binder mixture.
 20. Asystem for reducing the amount of a contaminant species in a feedstream, the system comprising: a column configured to contain a metalexchanged and impregnated zeolite material comprising: a metal exchangedzeolite material with the formula((M_(2/n)O)_(a)•(M′_(2/n′)O)_(a′))•Al₂O₃•bSiO₂; and a metal oxide withthe formula M_(2/n)O impregnated in the metal exchanged zeolite materialsuch that the metal oxide is contacting an interior surface of the porestructure of the metal exchange zeolite material; where M is a cation ofan alkali or alkaline earth metal, n is a valence state of metal cationM, M′ is a cation of a metal other than an alkali or alkaline earthmetal, n′ is a valence state of metal cation M′, 0≦a<1, 0<a′≦1, a+a′=1,and b is about 2 to about 500; wherein the column is configured toreceive and contact a feed stream with the metal impregnated zeolitematerial under conditions effective for at least a portion of acontaminant species in the feed stream to be adsorbed by the metalimpregnated zeolite material.